Fly911

What calipers would fit my '85 928S? I just saw a set of 964 front calipers on Pelican for $200... Will they fit on a 1985 928? Porsche used the same calipers on several different models, what brakes from what models could replace the single piston floating calipers? Will I need to change the MC like I did on my 911 when I went from the standard Carrera brakes to 930 brakes? What about the rotors, use the same or different? Would 993 brakes, or even 996/997 brakes fit? Any brake gurus here...?

The Forgotten On

You need a set of caliper adapters along with a set of the early spindles (78-81) to make it work.

Easiest and most effective upgrade you can do would to be to get a set of better pads.

There was a user @xschop who used to make caliper adapters for the S spindle but he hasn't been active in a while.

Speedtoys

What does the S4 upgrade need on this car?

GregBBRD

S4 upper and lower contol arms, ball joints, and spindles, plus S4 calipers and rotors..

928 International generally has these pieces, although they are likely going to need some "refreshing".

Rear S4 calipers bolt directly on.

Booster and master will work, if in good condition.

Darklands

But the ABS will be broken! :-( after the S4 parts. The ABS rings are different.

icsamerica

I went through all of this first hand when I 1/2'd my 86. I needed to change the complete front and rear uprights and spindles, that included front upper control arms and lower ball joints. The front sway bar links also needed to be changed. Out back on the rear axle, I changed the spindles complete and needed newer axles so the ABS tone wheel would match the front. The connections for the ABS wiring at the uprights were also different. Lucky for me the person who removed the spindles clipped the wiring at the body side so I had all the fixings. I was really surprised how different the suspension setup is. This wasn't an incremental change it was a redesign in many respects.

As for the ABS, I needed and used a later ABS (1987) computer becasue the count on the tone wheel is 1/2 what it is for the earlier cars. A close inspection and comparison of the pre and post 86.5 wiring harnesses indicated just 1 pin had to be relocated. Once that was done the ABS worked fine and as expected.

icsamerica

I recently met a guy at a 928 meet up that had them. He stated he got them and his 928 recently. I was surprised becasue I had tried to get the adapters in the past and called 2x times with no results. I mentioned this and he stated it wasn't' easy and he had to call many times. I think the phrase he used was "haunt the guy"

I have a 2 call limit. If I don't get results after 2x, I'm done and will just make the item myself. I'm still waiting for a call back on the billet shifter, looks like I'll be making my own there too.

Speedtoys

No ABS to being with..

GregBBRD

The issue with the "adapter approach" is that the early ball joint rubs on the brake rotor on compression.
Yes, the ball joint can be "ground on" enough to clear, however it gets fairly thin.

The S4 brake and suspension upgrade has several benefits.

Yes, you get bigger brakes...that's a given.

However, one of the biggest, yet frequently overlooked, benefits is that the lower ball joint is reversed in the S4 suspension. The ball is pushed into the socket, which is very stable.
In the pre-S4 suspension, the ball is continuously being pulled out of the sockets weaker edges.

Major upgrade in design.

Landseer

I've also done the full swap. Put 86.5/S4 suspension and brakes onto 84 car. This was a time consuming upgrade. But I felt better with the factory upgrade instead instead of adapters. It's a lot of parts.

I also swapped the brake bias valve.

I know the 944 turbo brakes are same. Not sure about 964. Cant remember if, on caliper and adapter swap, if rotor change is needed. A good search will find that answer, it's been covered here before.

The Forgotten On

The 964 C2 has the same front caliper as an S4, but the rears are generally 2 piston instead of 4.

You can get the rears from a 993. They bolt on the same as the S4 but have larger pistons so you get extra clamping force.

Strosek Ultra

https://perfexmfg.com/s-big-brake-adapter-bracket-kit/

The Forgotten On

^^ If you get D2 Audi S8 calipers you can use the 350mm Cayenne rotor. It uses GTS pads and is otherwise identical.

A used set can usually be had for $400.

zekgb

Has anyone actually confirmed fitment with the Perfex adapter and the D2's? If so that seems like a damned good option.

The Forgotten On

It fits with the normal adapter for the 78-81 as the caliper bolt spacing is the same, but the holes are 4mm back compared to where they need to be so it wont clear the 993 rotor.

The Perfex adapter accounts for this as it was made with the Cayenne rotors in mind (the D2s have the same offset as the S4, GTS, etc.) so it will fit.

The D2 also bolts up to the factory S4 hub, but you need 350mm rotors with a S4 rotor offset to make it work so there is no cheap off the shelf rotor option.

For reference, the depth on a Cayenne rotor is 69mm hat to back of rotor face, a 993 is 73, and the S4/GTS is 77.

You also need a set of longer caliper bolts. Panamera Part #999 067 040 01 works perfectly for this.

Also, shout out and thank you to @Jerry Feather for the hubcentric rings, they fit perfectly after a touch of sanding.